Method for the optimization of the conditions of execution of the vision contrast test, and corresponding system

ABSTRACT

Described herein is a method for optimization of the conditions of execution of the vision contrast test and the corresponding system with which to implement said method so as to be able to guarantee optimal conditions throughout the test session even when not it is not possible to respect the standards. Furthermore, the method comprises a self-calibration procedure, which definitively eliminates the operations of calibration of the system by specialized centres.

FIELD OF THE INVENTION

The present invention relates to a method for optimization of theconditions of execution of the vision contrast test and correspondingsystem.

PRIOR ART

During optical or oculistic examinations, in order to explore particularfunctions of the visual apparatus, amongst which visual acuity insituations of controlled contrast, it is necessary to subject thepatient to visual stimuli with different and calibrated contrasts inbinocular vision.

Current computerized systems normally use LCDs, which undergocalibration in the factory, possibly repeated periodically in thelaboratory, to guarantee a yield of the basic brightness that is correctfor use of particular levels of brightness in the contrast test.

One problem lies in the intrinsic inconstancy of the brightness of thedisplay device (hereinafter simply referred to as “display”), which istypically obtained using LCD technology, and in particular of thecorresponding backlighting system. Many of the tests must provide acertification of the results, which is markedly affected by theconstancy and the verifiability of the calibration and by the use of thecorrect ambient illumination.

Another, even more important, problem lies in the impossibility ofcontrolling illumination of the environment in which the test isconducted, with consequent influence on the results of the test, whichis based upon the perception of the brightness (luminance) and of thecontrasts of the display system.

In the use of conventional optotypes, a manual control of the ambientlight is used, aimed at obtaining an illumination of the environmentthat is constant during the tests. Unfortunately, however, the intensityof the light emitted by the light sources is never regulated in anabsolute sense in relation to the optimal level of illumination that thetesting environment should have.

Consequently, also tests that are based upon the display of computerizedoptotypes, which use LCDs, are not reliable in so far as theillumination of the environment is not only not precise, but may alsonot be adjustable, or may even vary while the test is being carried out,for example, on account of changes in the conditions of shading, andmoreover added to this is the inconstant calibration of the LCD.

SUMMARY OF THE INVENTION

Consequently, the purpose of the present invention is to overcome allthe aforesaid drawbacks and to indicate a system for managing at thesame time the conditions of illumination of the environment and ofbrightness of the display in addition to calibrating the emissionthereof in terms of white and colour balancing.

A further purpose of the present invention is to provide a method and acorresponding system definitively eliminating the need to subject thedisplay systems to periodic calibration.

Yet a further purpose of the present invention is to provide a systemintegrating a standard low-cost computer equipped with a display device.

Consequently, a particular object of the present invention is a methodfor optimization of the conditions of execution of the vision contrasttest.

BRIEF DESCRIPTION OF THE DRAWINGS

Further purposes and advantages of the present invention will emergeclearly from the ensuing detailed description of an example ofembodiment thereof (and of its variants) and from the annexed plates ofdrawings, which are provided purely by way of explanatory non-limitingexample and in which:

FIG. 1 is a flowchart representing the method;

FIG. 2 illustrates the block “Calibration of Ambient Illumination” ofthe diagram of FIG. 1;

FIG. 3 illustrates the block “Self-calibration of Display” of thediagram of FIG. 1; and

FIG. 4 represents the logic diagram of interconnection of the variousdevices making up the system.

DETAILED DESCRIPTION OF THE INVENTION

The method forming the subject of the present invention comprises thesteps described below in relation to precise conditions in accordancewith the flowchart represented in FIG. 1.

If a test on visual acuity is being carried out, the block “Calibrationof Ambient Illumination” is executed, and, by means of a signallingdevice, the goodness of the conditions of ambient illumination issignalled, according to the flowchart represented in FIG. 2.

If the standard conditions have been met, it is possible to carry outthe visual-acuity test (not appearing in the flowchart because it is initself known).

If the conditions have not been met, the operator is asked whether hewishes to carry out a certified examination (i.e., an examination thatrespects a standard in itself known). If the answer is “YES”, theprocedure ends (END block) because it is not possible to proceed anyfurther (for example, a red light lights up).

Otherwise, if it is not required to perform a certified examination, the“Adjust Display Emission” procedure is executed. Said procedurecomprises the following steps:

-   -   a. if the conditions of ambient illumination are higher than the        norm, then the brightness of the display is increased;    -   b. otherwise, if the conditions of ambient illumination are        lower than the norm, then the brightness of the display is        decreased;    -   c. if it is not possible to vary the brightness so as to obtain        an effective test session, then the event is signalled, for        example, with a red light, and the procedure starts again from        step a in order to provide a real-time and efficient adjustment        as any ambient condition varies;    -   d. if the adjustment has been successful, then the event is        signalled, for example, with a green light.

Preferably, the Adjustment Display Emission procedure is executed incontinuous mode, so as to provide a real time and efficient adjustmentas any ambient condition varies.

The aforementioned procedure of “Calibration of Ambient Illumination” isexecuted according to the following steps:

-   -   a. the level of ambient illumination is measured;    -   b. if the value of illumination is within a threshold S1, then        the event is signalled as positive and, for example, a green        light lights up;    -   c. if the conditions are within a threshold S2, then the event        is signalled as intermediate and, for example, a yellow light        lights up;    -   d. if the conditions are not within the threshold S2, then the        event is signalled as negative and, for example, a red light        lights up.

Preferably, the Calibration of Ambient Illumination procedure isexecuted in continuous mode, so as to provide a real time and efficientcalibration as any ambient condition varies. If a visual-acuity test isnot being carried out, but rather self-calibration of the display isrequired, then, once the reflecting dome has been mounted, operation ofwhich will be illustrated hereinafter, the system executes, in acompletely autonomous way, the self-calibration test in accordance withthe flowchart represented in FIG. 3; hence the complete process is thefollowing:

-   -   a. the reflecting dome is installed;    -   b. the colour-detection sensor is brought up to the display for        white balancing;    -   c. a sequence of images is projected, and the brightness and        colours emitted by the display are detected;    -   d. if necessary, the emission curve is corrected, and the        procedure returns to step b;    -   e. if the correction is not necessary, the procedure ends.

It is consequently clear that with the method described above it ispossible to regulate the conditions of ambient illumination andcalibrate the display to obtain certified tests on visual acuity of thepatient.

Furthermore, it is in any case possible to obtain efficient tests, eventhough they do not respect any standard, which are based upon thecompensation of the level of emission of the display in relation to theambient conditions.

A preferred embodiment of the system that enables implementation of saidmethod comprises (FIG. 4):

-   -   a display 1, for example, an LCD;    -   a microcomputer 2, for example, integrated in the package of the        display 1;    -   an illumination sensor 3, integrated in the frame of the display        1;    -   a colour-detection sensor 4, integrated in the frame of the        display 1;    -   a signalling device 5 with coloured LEDs (or multitone audio);    -   an interface 6, for example, a USB interface, for connection        between said microcomputer 2 and another computer;    -   a mirror dome or deflector 7; and    -   a standard computer 8.

The microcomputer 2 is connected to the sensors 3 and 4 and to thedevice 5 and has an interface 6.

The microcomputer 2 analyses the information obtained from the sensor 3and enables lighting-up of the signalling device 5 in according to theprocedure set forth above.

The microcomputer 2 is connected to the computer 8 by means of saidinterface 8 to enable modification of the control signals that thegraphic card of the computer 8 emits in driving the display 1, when itis not possible to respect the standard ambient conditions.Consequently, it is clear that the display 1 is connected to thecomputer 8.

In the self-calibration step, it is necessary to convey the brightnessemitted by the display onto the sensor 3, as likewise it is necessary tobring the sensor 4 up to the display to adjust white balancing so thatthe microcomputer can regulate, via the computer 8, the emission of thegraphic card with which the latter is equipped. Advantageously, use of adome or deflector 7 during self-calibration means that the sensor 4 isnot impinged upon by environmental light, but only by the light emittedby the display.

Lastly, in a preferred embodiment, said illumination sensor 3 is aTSL257-E35 manufactured by Texas Instruments, the intrinsiccharacteristics of construction of which guarantee its reliability, butabove all robustness of the system in regard to disturbance on thesupply and/or deriving from the environmental climatic conditions, sothat the factory calibration of the circuitry that drives said componentguarantees perfect behaviour of the system throughout its service life,without calling for any further intervention. It is clear that the factof entrusting calibration of the display 1 to a sensor 4 of extremelyhigh precision as compared to the precision of the device 1 radicallysolves the problem of maintenance interventions.

During the calibration step, the software that manages the microcomputerdrives the computer 8, by means of its own graphic card, to displayparticular sequences of images appropriately composed, for the purposeof a better correction of the emission curve of the display in terms ofbrightness, contrast, red, blue, and green balancing.

The present invention can advantageously be implemented via a computerprogram, which comprises code means for implementation of part or allthe steps of the method, when the program is run on a computer.Consequently, it is understood that the scope of protection extends tosaid computer program and moreover to computer-readable means, whichcomprise a recorded message, said computer-readable means comprisingprogram-code means for the implementation of one or more steps of themethod, when said program is run on a computer.

Variant embodiments of the non-limiting example described are possible,without thereby departing from the scope of protection of the presentinvention, including all the equivalent embodiments that can be made bya person skilled in the art.

1. A system for optimizing the conditions of execution of the vision contrast test, comprising: a display device (1); a microcomputer (2); an illumination sensor (3); colour-detection sensor (4); a signalling device (5); a connection interface (6); a mirror dome or deflector (7); and a computer (8), equipped with a graphic card.
 2. The system according to claim 1, characterized in that said microcomputer (2) is connected to said illumination sensor (3), to said colour-detection sensor (4), and to a connection interface (6).
 3. The system according to claim 1, characterized in that the display device (1) is an LCD.
 4. The system according to claim 1, characterized in that the signalling device (5) has coloured lights;
 5. The system according to claim 1, characterized in that the signalling device (5) has a multitone buzzer.
 6. The system according to claim 1, characterized in that the connection interface is of a USB or RS232 type, or the like.
 7. The system according to claim 6, characterized in that any adjustment of the emission of the display (1) is driven by the microcomputer through the USB interface, via said computer (8), given that the graphic card of said computer (8) is connected to said display (1).
 8. A method for optimization of the conditions of execution of the vision contrast test, comprising the following steps: a. if a visual-acuity test is being carried out, the block “Calibration of Ambient Illumination” is executed; b. if the “Calibration of Ambient Illumination” procedure is unsuccessful and a certified examination is not requested, then the “Adjust Display Emission” procedure is executed; c. otherwise, if a certified examination is requested or if it is not possible to complete the “Adjust Display Emission” procedure the program exits from the main procedure yielding a negative result; d. otherwise, if a visual-acuity test is not being carried out, the “Self-calibration” procedure is executed.
 9. The method according to claim 8, characterized in that the “Calibration of Ambient Illumination” procedure comprises the following steps: a. the level of illumination of the environment is measured; b. if the value of illumination is within a threshold S1, then the event is signalled as positive; c. if the conditions are within a threshold S2, then the event is signalled as intermediate; d. if the conditions are not within the threshold S2, then the event is signalled as negative.
 10. The method according to claim 8, characterized in that the “Adjust Display Emission” procedure comprises the following steps: a. if the conditions of ambient illumination are higher than the norm, then the brightness of the display device is increased; b. otherwise, if the conditions of ambient illumination are lower than the norm, then the brightness of the display device is decreased; c. if it is not possible to vary the brightness so as to obtain an effective test session, the event is signalled accordingly; d. if the adjustment has been successful, the event is signalled accordingly.
 11. The method according to claim 8, characterized in that the “Self-calibration” procedure comprises the following steps: a. the reflecting dome is set in position; b. the colour-detection sensor is set in position; c. a sequence of images is projected; simultaneously, the brightness and colours emitted by the display device are detected; d. if necessary, the emission curve is corrected, and the procedure returns to step b; e. if a correction is not necessary, the procedure ends. 